Electronic camera having continuous shooting function

ABSTRACT

An electronic camera having a continuous shooting function includes: an image capturing unit that captures a subject image; a setting unit that sets operating parameters related to image processing performed during image capturing; a resolution conversion unit that performs resolution conversion on image data of an image captured by the image capturing unit in correspondence to a resolution set at the setting unit; an image compression unit that performs image compression on image data converted by the resolution conversion unit in correspondence to a compression factor set at the setting unit; and a continuous shooting unit that performs continuous shooting of a subject image by continuously driving the image capturing unit, the resolution conversion unit and the image compression unit. And: the resolution conversion unit is capable of performing resolution conversion at least at a high resolution and at a low resolution that is lower than the high resolution; the image compression unit is capable of performing image compression at least at a low compression factor and at a high compression factor that is higher than the low compression factor; and when the continuous shooting unit executes continuous shooting, the image compression unit performs image compression at the high compression factor if the resolution at the resolution conversion unit is set to the low resolution.

INCORPORATION BY REFERENCE

[0001] The disclosure of the following priority application is hereinincorporated by reference: Japanese Patent Application No. 10-61013,filed Mar. 12, 1998

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an electronic camera having acontinuous shooting function. More specifically, the present inventionrelates to an electronic camera capable of achieving higher speed incontinuous shooting.

[0004] 2. Description of the Related Art

[0005] The technologies for achieving a higher speed in continuousshooting in electronic cameras in the known art include the following.Japanese Laid-Open Patent Publication No. H6-54252 discloses atechnology whereby the continuous shooting speed is increased bysimultaneously performing exposure of the subsequent frame on the imagecapturing element side while compressing the image in the precedingframe.

[0006] Japanese Laid-Open Patent Publication No. H5-191700 discloses atechnology whereby the length of the image read time is reduced byreading out an image signal every few lines from the image capturingelement to achieve higher speed in continuous shooting. JapaneseLaid-Open Patent Publication No. H7-135589 discloses a technologywhereby the length of the image recording time is reduced by dividingthe data of an image that has been captured to be recorded onto aplurality of recording media to achieve a higher speed in continuousshooting.

[0007] The following problems arise with the prior art technologiesdescribed above.

[0008] In regard to the technology disclosed in Japanese Laid-OpenPatent Publication No. H6-54252, if the exposure time is longer than thelength of time required for compression processing, the exposureoperation and the compression processing operation are executedcontinuously with a high degree of efficiency. As a result, the fulladvantage can be achieved. However, if the exposure time is shorter thanthe compression processing time, the image capturing element side mustremain in a standby state for the read of the image in the succeedingframe until the compression processing of the preceding frame iscompleted. Thus, the continuous shooting speed is reduced by the lengthof time corresponding to the wait time.

[0009] The technology disclosed in Japanese Laid-Open Patent PublicationNo. H5-191700 requires the use of a special image capturing element thatis capable of reading out the horizontal lines by specifying individuallines and thus presents a problem in that a general-purpose imagecapturing element cannot be utilized.

[0010] The technology disclosed in Japanese Laid-Open Patent PublicationNo. H7-135589, which requires a mechanism for mounting a plurality ofrecording media and recording circuits, makes it difficult to achieveminiaturization of the electronic camera and a reduction in the cost.

SUMMARY OF THE INVENTION

[0011] An object of the present invention is to provide an electroniccamera capable of achieving higher speed in continuous shooting, whichis achieved through a different approach from those taken in the priorart technologies described above.

[0012] In order to attain the above object, an electronic camera havinga continuous shooting function according to the present invention,comprises: an image capturing unit that captures a subject image; asetting unit that sets operating parameters related to image processingperformed during image capturing; a resolution conversion unit thatperforms resolution conversion on image data of an image captured by theimage capturing unit in correspondence to a resolution set at thesetting unit; an image compression unit that performs image compressionon image data converted by the resolution conversion unit incorrespondence to a compression factor set at the setting unit; and acontinuous shooting unit that performs continuous shooting of a subjectimage by continuously driving the image capturing unit, the resolutionconversion unit and the image compression unit. And: the resolutionconversion unit is capable of performing resolution conversion at leastat a high resolution and at a low resolution that is lower than the highresolution; the image compression unit is capable of performing imagecompression at least at a low compression factor and at a highcompression factor that is higher than the low compression factor; andwhen the continuous shooting unit executes continuous shooting, theimage compression unit performs image compression at the highcompression factor if the resolution at the resolution conversion unitis set to the low resolution.

[0013] Another electronic camera having a continuous shooting function,comprises: an image capturing unit that captures a subject image; asetting unit that sets operating parameters related to image processingperformed during image capturing; a resolution conversion unit thatperforms resolution conversion on image data of an image captured by theimage capturing unit in correspondence to a resolution set at thesetting unit; an image compression unit that performs image compressionon image data converted by the resolution conversion unit incorrespondence to a compression factor set at the setting unit; and acontinuous shooting unit that performs continuous shooting of a subjectimage by continuously driving the image capturing unit, the resolutionconversion unit and the image compression unit. And: the resolutionconversion unit is capable of performing resolution conversion at leastat a high resolution and at a low resolution that is lower than the highresolution; the image compression unit is capable of performing imagecompression at least at a low compression factor and at a highcompression factor that is higher than the low compression factor; andwhen the continuous shooting unit executes continuous shooting, theresolution conversion unit performs resolution conversion at the lowresolution if the compression factor at the image compression unit isset to the high compression factor.

[0014] Another electronic camera having a continuous shooting function,comprises: an image capturing unit that captures a subject image; asetting unit that sets operating parameters related to image processingperformed during image capturing; a resolution conversion unit thatperforms resolution conversion on image data of an image captured by theimage capturing unit in correspondence to a resolution set at thesetting unit; an image compression unit that performs image compressionon image data converted by the resolution conversion unit incorrespondence to a compression factor set at the setting unit; and acontinuous shooting unit that performs continuous shooting of a subjectimage by continuously driving the image capturing unit, the resolutionconversion unit and the image compression unit. And: the setting unit iscapable of setting a continuous shooting speed at the continuousshooting unit at least at a normal speed and at a high speed that ishigher than the normal speed; the resolution conversion unit is capableof performing resolution conversion at least at a high resolution and ata low resolution that is lower than the high resolution; the imagecompression unit is capable of performing image compression at least ata low compression factor and a high compression factor that is higherthan the low compression factor; and when the continuous shooting unitexecutes continuous shooting, the resolution conversion unit performsresolution conversion at the low resolution and the image compressionunit performs image compression at the high compression factor if thecontinuous shooting speed is set to the high speed.

[0015] Another electronic camera having a continuous shooting function,comprises: an image capturing unit that captures a subject image; asetting unit that sets operating parameters related to image processingperformed during image capturing; a resolution conversion unit thatperforms resolution conversion on image data of an image captured by theimage capturing unit in correspondence to a resolution set at thesetting unit; an image compression unit that performs image compressionon image data converted by the resolution conversion unit incorrespondence to a compression factor set at the setting unit; and acontinuous shooting unit that performs continuous shooting of a subjectimage by continuously driving the image capturing unit, the resolutionconversion unit and the image compression unit. And: the resolutionconversion unit is capable of performing resolution conversion at leastat a high resolution and at a low resolution that is lower than the highresolution; the image compression unit is capable of performing imagecompression at least at a low compression factor and at a highcompression factor that is higher than the low compression factor; andwhen the continuous shooting unit executes continuous shooting, theresolution conversion unit performs resolution conversion at the lowresolution and the image compression unit performs image compression atthe high compression factor.

[0016] In each of the above electronic cameras having a continuousshooting function, preferably, an instruction unit that issuesinstructions to ensure that the resolution conversion unit performsresolution conversion at the low resolution and the image compressionunit performs image compression at the high compression factor, withouthaving to change settings for the resolution and the compression factorthat have been set by the setting unit, is provided; and when thecontinuous shooting unit executes continuous shooting, the resolutionconversion unit performs resolution conversion at the low resolution andthe image compression unit performs image compression at the highcompression factor in conformance to instructions issued at theinstruction unit.

[0017] It is to be noted in each of the above electric cameras thatdescriptions of “high compression factor”, “low resolution” and “highspeed” do not always mean “the highest compression factor”, “the lowestresolution” and “the highest speed”, respectively. Among these options,they mean “compression factor at a high compression factor side”,“resolution at a low resolution side” and “speed at a high speed side”,respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a block diagram illustrating the structure of anembodiment;

[0019]FIG. 2 is a flowchart illustrating the main routine executedduring photographing;

[0020]FIG. 3 is a flowchart illustrating the mode setting operation;

[0021]FIG. 4 is a flowchart illustrating the single-shot operation;

[0022]FIG. 5 is a flowchart illustrating the continuous shootingoperation; and

[0023]FIG. 6 is a flowchart illustrating the high-speed continuousshooting operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] The following is an explanation of an embodiment of the presentinvention given in reference to the drawings.

[0025]FIG. 1 is a block diagram illustrating the structure of theelectronic camera in this embodiment. In FIG. 1, a photographic opticalsystem 11 is provided inside the main body of the electronic camera. Onthe side of the photographic optical system 11 where the image space ispresent, the image capturing surface of a CCD image capturing element 13is provided. The CCD image capturing element 13 is driven by a controlpulse supplied by a CCD drive circuit 13 a. An analog image signal fromthe CCD image capturing element 13 is provided to an image processingcircuit 15 as digital image data after going through an A/D conversioncircuit 14. The image processing circuit 15 manages the overall imageprocessing achieved by the hardware, including the image compressionprocessing and the image synthesis processing for monitor display.

[0026] The image data for monitor display output from the imageprocessing circuit 15 are displayed on a liquid crystal monitor 15 a viaa liquid crystal drive circuit (not shown). A timing signal forindicating the drive timing of the CCD image capturing element 13 istransmitted from the image processing circuit 15 to the CCD drivecircuit 13 a. A control signal is provided to the image processingcircuit 15 by a CPU 16.

[0027] The CPU 16 performs exchange of image data with an image data busof the image processing circuit 15, a memory 18 and a flash memory card19, via a system bus 17. An operating button group 21 that includes ashutter release button 22, a menu button 23 and a zoom button 24 isconnected to the CPU 16.

[0028] In the actual circuit, the CPU 16 described above is constitutedas a multi-processor comprising a processor for image processing thatmanages the overall image processing by software and a processor forsystem control that monitors the operating buttons and the like at theelectronic camera.

[0029] In this embodiment, the CCD image capturing element 13 and theCCD drive circuit 13 a constitute an image capturing unit, the operatingbutton group 21 and the “function of setting various operatingparameters” achieved by the CPU 16 constitute a setting unit, the“function of achieving resolution conversion (or changing) for imagedata” achieved by the image processing circuit 15 constitutes aresolution conversion unit, the “function of performing imagecompression of image data” achieved by the image processing circuit 15constitutes an image compression unit and the “function of executingcontinuous shooting by controlling the image processing circuit 15 andthe CCD drive circuit 13 a” achieved by the CPU 16 constitutes acontinuous shooting unit.

[0030] It is to be noted that the function of changing the settingsrelated to image compression or resolution conversion is achievedthrough the “function of automatically setting the high-speed continuousshooting mode as part of the mode setting operation” of the CPU 16.

Main Routine in the Embodiment

[0031] The following is an explanation of the operation performed in theembodiment.

[0032]FIG. 2 is a flowchart illustrating the main routine executedduring photographing in the embodiment. First, the CPU 16 makes adecision as to whether or not an input operation for mode setting hasbeen performed through the operating button group 21 (FIG. 2 S1).

[0033] An input operation for mode setting in this context may be, forinstance, an operation during which the menu button 23 in the operatingbutton group 21 is pressed down for 0.2 seconds or longer. When such aninput operation is performed, the CPU 16 proceeds to execute the modesetting operation shown in FIG. 3 (FIG. 2 S2). If no input operation hasbeen performed, the CPU 16 makes a decision as to whether or not theshutter release button 22 has been pressed (FIG. 2 S3). Until theshutter release button 22 is pressed, the CPU 16 returns to theoperation in step S1 to standby for the mode setting operation.

[0034] Once the shutter release button 22 is pressed, (FIG. 2 S3 YES),the CPU 16 makes a decision in regard to the setting status for thephotographing mode (FIG. 2 S4). If the single-shot mode is set for thephotographing mode, the CPU 16 proceeds to execute the single shotoperation shown in FIG. 4 (FIG. 2 S5). If the continuous shooting modehas been set, the CPU 16 proceeds to execute the continuous shootingoperation in FIG. 5 (FIG. 2 S6).

[0035] If high-speed continuous shooting mode has been set, the CPU 16proceeds to execute the high-speed continuous shooting operation in FIG.6 (FIG. 2 S7). When this sequence of operations is completed, the CPU 16returns to step S1 in preparation for the next mode setting operationand the next operation in which the shutter release button 22 ispressed.

[0036] It is to be noted that the “single-shot mode” in this contextrefers to a normal mode in which one photographic frame is photographedin response to an operation in which the shutter release button 22 ispressed once and that the “continuous shooting mode” refers to a mode inwhich a plurality of photographic frames are continuously photographedat a constant rate while the shutter release button 22 is held down. The“high-speed continuous shooting mode” is a mode in which continuousshooting is performed at a higher speed compared to that in the“continuous shooting mode.”

[0037] Next, the operating routines described above are individuallyexplained.

Mode Setting Operation

[0038]FIG. 3 is a flowchart illustrating the mode setting operation.After the mode setting operation starts, the CPU 16 displays a menu listscreen on the liquid crystal monitor 15 a via the image processingcircuit 15. The operator operates the zoom button 24 to move the cursorposition in the screen and operates the shutter release button 22 toselect an appropriate menu item, having positioned the cursor. Byrepeating this type of interactive operation, a mode setting operationfor setting various modes is executed. During the execution of the modesetting operation, the zoom button 24 is used as a cursor positioningbutton and the shutter release button 22 is used as a selection decidingbutton, with their original zoom and shutter release functionsprohibited.

[0039] The following is an explanation of three types of mode settingoperations, i.e., “resolution setting”, “compression factor setting” and“continuous shooting setting”.

(1) Resolution Setting Operation

[0040] When the menu item “resolution setting” is selected (FIG. 3 S11YES), the CPU 16 displays the options, “high resolution mode” and “lowresolution mode” in the menu (FIG. 3 S12). At this point, if the “highresolution mode” is selected in the menu, the CPU 16 first sets aninternal flag at the image processing circuit 15 to the high resolutionmode (FIG. 3 S13) and then returns to the main routine in FIG. 2.

[0041] If the “low resolution mode” is selected in the menu, the CPU 16first sets the internal flag at the image processing circuit 15 to thelow resolution mode (FIG. 3 S14). With the low resolution mode set inthis manner, the CPU 16 makes a decision as to whether or not thesingle-shot mode has been set (FIG. 3 S15). If the single-shot mode hasbeen set (FIG. 3 S15 YES), the CPU 16 directly returns to the mainroutine in FIG. 2. If a mode other than the single-shot mode (thecontinuous shooting mode or the high-speed continuous shooting mode) hasbeen set (FIG. 3 S15 NO), the CPU 16 first changes the setting of theinternal flag at the image processing circuit 15 to high-speedcontinuous shooting mode (FIG. 3 S16) and then returns to the mainroutine in FIG. 2. Through the operation described above, the settingfor the resolution mode is completed.

[0042] It is to be noted that the “high resolution mode” in this contextrefers to a mode in which the data of an image that has been captured bythe CCD image capturing element 13 are used with the number of pixelsunchanged without thinning the pixels. The “low resolution mode” refersto a mode in which the pixels in the data of an image captured by theCCD image capturing element 13 are thinned at a specific rate to useimage data having a reduced number of pixels.

(2) Compression Factor Setting Operation

[0043] When the menu item “compression factor setting” is selected (FIG.3 S17 YES), the CPU 16 displays the options, “low compression mode” and“high compression mode” in the menu (FIG. 3 S18). If the “lowcompression mode” is selected in the menu, the CPU 16 first sets theinternal flag at the image processing circuit 15 to the low compressionmode (FIG. 3 S19), and then returns to the main routine in FIG. 2. It isto be noted that the low compression mode in this context refers to amode in which an appropriate low compression factor is set to assure thequality of the image.

[0044] If the “high compression mode” is selected in the menu, the CPU16 sets the internal flag at the image processing circuit 15 to the highcompression mode (FIG. 3 S20). It is to be noted that the highcompression mode in this context refers to a mode in which anappropriate high compression factor is set, mainly for the purpose ofreducing the length of the image transfer time.

[0045] As the high compression mode is set in this manner, the CPU 16makes a decision as to whether or not the single-shot mode has been set(FIG. 3 S21). If the single-shot mode has been set (FIG. 3 S21 YES) theCPU 16 directly returns to the main routine in FIG. 2. If, on the otherhand, a mode other than the single-shot mode (the continuous shootingmode or the high speed continuous shooting mode) has been set (FIG. 3S21 NO), the CPU 16 first changes the setting of the internal flag atthe image processing circuit 15 to the high-speed continuous shootingmode (FIG. 3 S22) and then returns to the main routine in FIG. 2.Through the operation described above, the setting of the compressionmode is completed.

(3) Continuous Shooting Setting Operation

[0046] When the menu item “continuous shooting setting” is selected(FIG. 3 S23 YES), the CPU 16 displays options, the “high-speedcontinuous shooting mode” and the “continuous shooting mode” in the menu(FIG. 3 S24). If the “high-speed continuous shooting mode” is selectedin the menu, the CPU 16 first sets the internal flag at the imageprocessing circuit 15 to the high-speed continuous shooting mode (FIG. 3S25) and returns to the main routine in FIG. 2.

[0047] If the “continuous shooting mode” is selected in the menu, theCPU 16 sets the internal flag at the image processing circuit 15 to thecontinuous shooting mode (FIG. 3 S26). As the continuous shooting modeis set in this manner, the CPU 16 first changes the setting of theinternal flag at the image processing circuit 15 to the high resolutionmode (FIG. 3 S27, S28) and then returns to the main routine in FIG. 2.Through the operation described above, the setting of the continuousshooting mode is completed.

Single Shot Operation

[0048]FIG. 4 is a flowchart illustrating the single shot operation.

[0049] After the single shot operation starts, the CPU 16 makes adecision as to whether or not photographing is enabled by verifying thebattery state, the quantity of electrical charge at the strobe, theremaining capacity in the flash memory card 19 and the like (FIG. 4S31).

[0050] If a decision is made that photographing is disabled (FIG. 4 S31NO), the CPU 16 displays a warning to that effect on the liquid crystalmonitor 15 a and then returns to the main routine in FIG. 2. If it isdecided that photographing is enabled (FIG. 4 S31 YES), the CPU 16 takesin image data from the CCD image capturing element 13 and calculates thecorrect aperture value, the correct exposure time and the quantity ofcontrast (FIG. 4 S32).

[0051] Based upon the contrast quantity thus calculated, the CPU 16moves the photographic optical system 11 backward and forward to executethe scanning and contrast detecting type AF control (FIG. 4 S33). Whenthe AF control is completed, the CPU 16 adjusts the aperture diameter ofthe photographic optical system 11 (also used as the lens shutter) incorrespondence to the correct aperture value (FIG. 4 S34). Followingthese preparations, the CPU 16 wipes or discharges all unnecessaryelectrical charge at the CCD image capturing element 13 via the CCDdrive circuit 13 a, to start photoelectric storage of a new image of thesubject (FIG. 4 S35).

[0052] When the correct exposure time has elapsed in this state, the CPU16 closes the lens shutter of the photographic optical system 11 to endthe photoelectric storage of the subject image (FIG. 4 S36).

[0053] In the following step, the CPU 16 reads out the image data fromthe CCD image capturing element 13 via the CCD drive circuit 13 a (FIG.4 S37). The image data thus read out are first digitized via the A/Dconversion circuit 14 and are then taken into the image processingcircuit 15. The image processing circuit 15 temporarily stores the imagedata in the memory 18.

[0054] If the high resolution mode has been set in advance (FIG. 4 S38NO), the image processing circuit 15 does not execute resolutionconversion (or changing) since the data of the captured image are usedwith the number of the pixels unchanged, without thinning any pixels.If, on the other hand, the low resolution mode has been set in advance(FIG. 4 S38 YES), the image processing circuit 15 thins out some pixelsfrom the image data in the memory 18 to reduce the resolution (FIG. 4S39).

[0055] Next, the image processing circuit 15 undertakes processing suchas DCT (discrete cosine transfer), quantization and variable lengthencoding before it executes image compression for the image data. If thelow compression mode has been set in advance (FIG. 4 S40 NO), the imageprocessing circuit 15 performs image compression for the image data byusing a quantizing table for a low compression factor (FIG. 4 S41). If,on the other hand, the high compression mode has been set in advance(FIG. 4 S40 YES), the image processing circuit 15 performs imagecompression for the image data by using a quantizing table for a highcompression factor (FIG. 4 S42).

[0056] After filing the image data that have been compressed in thismanner, the CPU 16 stores the filed image data in the flash memory card19 (FIG. 4 S43). Through the sequence of operations described above, thesingle shot operation is completed.

Continuous Shooting Operation

[0057]FIG. 5 is a flowchart illustrating the continuous shootingoperation. It is to be noted that the operation performed at S51˜S63 inFIG. 5 are identical to that in the single shot operation explainedearlier (FIG. 4 S31˜S43). In this embodiment, the continuous shootingoperation is executed by repeating an operation (FIG. 5 S52˜S63)identical to that in the single shot operation. The CPU 16 ends thecontinuous shooting operation as soon as the pressure on the shutterrelease button 22 is released (FIG. 5 S65) to return to the main routinein FIG. 2.

[0058] If the remaining capacity at the flash memory card 19 becomesinsufficient during such a continuous shooting operation (FIG. 5 S64),the CPU 16 immediately interrupts the continuous shooting operation toreturn to the main routine in FIG. 2.

High-Speed Continuous Shooting Operation

[0059]FIG. 6 is a flowchart illustrating the high-speed continuousshooting operation. When the high-speed continuous shooting operationstarts, the CPU 16 makes a decision as to whether or not photographingis enabled by checking the battery state, the quantity of the electricalcharge at the strobe, the remaining capacity at the flash memory card 19and the like (FIG. 6 S71).

[0060] If a decision is made that photographing is disabled (FIG. 6 S71NO), the CPU 16 displays a warning to that effect on the liquid crystalmonitor 15 a and then returns to the main routine in FIG. 2. If it isdecided that photographing is enabled (FIG. 6 S71 YES), the CPU 16calculates the correct aperture value, the correct exposure time and thequantity of contrast based upon image data obtained from the CCD imagecapturing element 13 (FIG. 6 S72).

[0061] Based upon the contrast quantity thus calculated, the CPU 16moves the photographic optical system 11 backward and forward to executethe scanning and contrast detecting type AF control (FIG. 6 S73). Whenthe AF control is completed, the CPU 16 adjusts the aperture diameter ofthe photographic optical system 11 (also used as the lens shutter) incorrespondence to the correct aperture value (FIG. 6 S74). Followingthese preparations, the CPU 16 wipes or discharges all the unnecessaryelectrical charge at the CCD image capturing element 13 via the CCDdrive circuit 13 a, to start a new photoelectric storage of the image ofthe subject (FIG. 6 S75).

[0062] When the correct length of exposure time has elapsed in thisstate, the CPU 16 closes the lens shutter at the photographic opticalsystem 11 and ends the photoelectric storage of the subject image (FIG.6 S76). The CPU 16 reads out the image data from the CCD image capturingelement 13 via the CCD drive circuit 13 a (FIG. 6 S77). The image datathus read out are first digitized via the A/D conversion circuit 14 andare then taken into the image processing circuit 15. The imageprocessing circuit 15 temporarily stores the image data in the memory18.

[0063] The image processing circuit 15 reduces the resolution of theimage data in the memory 18 regardless of the resolution mode that hasbeen set in advance (FIG. 6 S78). Next, the image processing circuit 15performs image compression for the image data in the memory 18 at thehigh compression factor regardless of the compression mode that has beenset in advance (FIG. 6 S79).

[0064] After filing the image data that have been compressed in thismanner, the CPU 16 temporarily stores the filed image data in a bufferarea provided in the memory 18.

[0065] By repeating this sequence of operations (FIG. 6 S72˜S80), thehigh-speed continuous shooting operation is executed. If the pressure onthe shutter release button 22 is released during such a high-speedcontinuous shooting operation (FIG. 6 S83), the CPU 16 first transfersthe image files in the buffer area to the flash memory card 19 in abatch for recording (FIG. 6 S84) and then returns to the main routine inFIG. 2.

[0066] In addition, if the remaining capacity at the flash memory card19 is anticipated to become insufficient (FIG. 6 S81) or if the buffercapacity of the memory 18 becomes insufficient (FIG. 6 S82) during thehigh-speed continuous shooting operation, the CPU 16 immediatelytransfers the image files in the buffer area to the flash memory card 19in a batch for recording (FIG. 6 S84) and then returns to the mainroutine in FIG. 2. Through the sequence of operations described above,the high-speed continuous shooting operation is completed.

[0067] With the operation in the embodiment achieved as described above,if the operator performs a setting operation to set the low resolutionmode while the continuous shooting mode is set, the mode is reset to thehigh-speed continuous shooting mode automatically (see FIG. 3 S15, S16).In the high-speed continuous shooting mode, image compression isperformed at the high compression factor regardless of the compressionmode setting (see FIG. 6 S79). Thus, the quantity of data after DCTquantization during the image compression processing is reduced so thatthe length of time required for variable length encoding and the likecan be reduced. In addition, since the image data quantity after thecompression is bound to be small, the length of time required for imagerecording in the memory 18 can be reduced. For these reasons, the lengthof time required for photographing one frame is reduced, thereby makingit possible to achieve a higher speed in continuous shooting with aneven higher degree of reliability.

[0068] If, on the other hand, the operator performs an operation to setthe high resolution mode while the continuous shooting mode is set, themode is not necessarily reset to the high-speed continuous shooting mode(see FIG. 3 S13). In this case, since the resolution conversion and theimage compression are executed in conformance to the mode setting, it isalso possible to execute continuous shooting of high quality images athigh resolution with a low compression factor.

[0069] In this embodiment, if the operator performs an operation to setthe high compression mode while the continuous shooting mode is set, themode is automatically reset to the high-speed continuous shooting mode(see FIG. 3 S21, S22). In the high-speed continuous shooting mode, theimage data are converted with low resolution regardless of the settingfor the resolution mode (see FIG. 6 S78). Thus, the amount of arithmeticprocessing to be performed for the image compression is reduced toachieve a reduction in the length of compression processing time.Furthermore, with the quantity of image data reduced after thecompression, the length of time required for image recording, too, isreduced. For these reasons, the length of time required forphotographing a given frame is reduced so that a higher speed incontinuous shooting is achieved with an even higher degree ofreliability.

[0070] If the operator performs an operation for setting the lowcompression mode while the continuous shooting mode is set, the mode isnot necessarily reset to the high-speed continuous shooting mode (seeFIG. 3 S19). In this case, since the resolution conversion and the imagecompression are executed in conformance to the mode settings, it is alsopossible to execute continuous shooting of images of high quality at thehigh resolution and the low compression factors.

[0071] In the embodiment, the operator may directly select thehigh-speed continuous shooting mode (FIG. 3 S25). In this high-speedcontinuous shooting mode, the image data are converted with a lowresolution and a high compression factor regardless of the settings forthe resolution mode and the compression mode (see FIG. 6 S78, S79).Thus, a higher speed in continuous shooting is achieved with a higherdegree of reliability by reducing the length of time required forcompression processing and the length of time required for imagerecording.

[0072] In addition, the operator may directly select the continuousshooting mode. Since the resolution conversion and the image compressionare executed in conformance to the mode settings in this case, it isalso possible to execute continuous shooting of high quality images atthe high resolution and at the low compression factors.

[0073] In the embodiments, when setting the high-speed continuousshooting mode, the settings for the compression mode and the resolutionmode at that point, are maintained unchanged. Consequently, when thehigh-speed continuous shooting mode is cleared, the operation candirectly return to the original compression mode and resolution mode.This operation eliminates the necessity for resetting the compressionmode and the resolution mode when the high-speed continuous shootingmode is cleared, to further improve the operability of the electroniccamera.

[0074] It is to be noted that while the high-speed continuous shootingmode is automatically set during a mode setting operation, the presentinvention is not limited to this example. For instance, the imageprocessing circuit 15 may forcibly execute image processing in the lowresolution mode (or the high compression mode) if the high compressionmode (or the low resolution mode) is set in the continuous shootingprocessing routine. Through such an operation, too, a higher speed incontinuous shooting can be realized with a high degree of reliability.

[0075] In addition, in the embodiment described above, continuousshooting is possible in two different modes, i.e., the continuousshooting mode and the high-speed continuous shooting mode. Theembodiment assumes a structure in which, if the high compression mode orthe low resolution mode is set while the “continuous shooting mode” isset, the mode is automatically switched to the “high-speed continuousshooting mode”. However, the present invention is not limited to thisstructural example. For instance, there may be only one mode forcontinuous shooting to perform high-speed continuous shooting when thehigh compression mode or the low resolution mode is set and to performlow-speed continuous shooting in other cases. Namely, the photographermay have a choice only as to whether or not continuous shooting is to beperformed, with high-speed continuous shooting automatically performedif the high compression mode or the low resolution mode is set andlow-speed continuous shooting performed under other conditions. In thiscase, only the processing in which the internal flag is set to the“continuous shooting mode” in step S26 among steps S24˜S28 in FIG. 3needs to be performed without having to select a menu item forcontinuous shooting setting.

[0076] Furthermore, if there is only one mode available for thecontinuous shooting, high-speed continuous shooting may beunconditionally performed if the “continuous shooting mode” is selected.In this case, only the processing for setting the internal flag to the“high-speed continuous shooting mode” in step S25 needs to be performedamong steps S24˜S28 in FIG. 3.

[0077] Moreover, while continuous shooting is started up by pressingdown the shutter release button 22 while the “continuous shooting mode”or the “high-speed continuous shooting mode” is set in the embodimentdescribed above, the startup operation for continuous shooting in thepresent invention is not limited to this example. For instance,continuous shooting may be started up and continued in response to asustained pressure on the shutter release button 22.

What is claimed is;
 1. An electronic camera having a continuous shootingfunction, comprising: an image capturing unit that captures a subjectimage; a setting unit that sets operating parameters related to imageprocessing performed during image capturing; a resolution conversionunit that performs resolution conversion on image data of an imagecaptured by said image capturing unit in correspondence to a resolutionset at said setting unit; an image compression unit that performs imagecompression on image data converted by said resolution conversion unitin correspondence to a compression factor set at said setting unit; anda continuous shooting unit that performs continuous shooting of asubject image by continuously driving said image capturing unit, saidresolution conversion unit and said image compression unit, wherein:said resolution conversion unit is capable of performing resolutionconversion at least at a high resolution and at a low resolution that islower than the high resolution; said image compression unit is capableof performing image compression at least at a low compression factor andat a high compression factor that is higher than the low compressionfactor; and when said continuous shooting unit executes continuousshooting, said image compression unit performs image compression at thehigh compression factor if the resolution at said resolution conversionunit is set to the low resolution.
 2. An electronic camera having acontinuous shooting function according to claim 1, wherein: aninstruction unit that issues instructions to ensure that said resolutionconversion unit performs resolution conversion at the low resolution andsaid image compression unit performs image compression at the highcompression factor, without having to change settings for the resolutionand the compression factor that have been set by said setting unit, isprovided; and when said continuous shooting unit executes continuousshooting, said resolution conversion unit performs resolution conversionat the low resolution and said image compression unit performs imagecompression at the high compression factor in conformance toinstructions issued at said instruction unit.
 3. An electronic camerahaving a continuous shooting function, comprising: an image capturingunit that captures a subject image; a setting unit that sets operatingparameters related to image processing performed during image capturing;a resolution conversion unit that performs resolution conversion onimage data of an image captured by said image capturing unit incorrespondence to a resolution set at said setting unit; an imagecompression unit that performs image compression on image data convertedby said resolution conversion unit in correspondence to a compressionfactor set at said setting unit; and a continuous shooting unit thatperforms continuous shooting of a subject image by continuously drivingsaid image capturing unit, said resolution conversion unit and saidimage compression unit, wherein: said resolution conversion unit iscapable of performing resolution conversion at least at a highresolution and at low resolution that is lower than the high resolution;said image compression unit is capable of performing image compressionat least at a low compression factor and at a high compression factorthat is higher than the low compression factor; and when said continuousshooting unit executes continuous shooting, said resolution conversionunit performs resolution conversion at the low resolution if thecompression factor at said image compression unit is set to the highcompression factor.
 4. An electronic camera having a continuous shootingfunction according to claim 3, wherein: an instruction unit that issuesinstructions to ensure that said resolution conversion unit performsresolution conversion at the low resolution and said image compressionunit performs image compression at the high compression factor, withouthaving to change settings for the resolution and the compression factorthat have been set by said setting unit, is provided; and when saidcontinuous shooting unit executes continuous shooting said resolutionconversion unit performs resolution conversion at the low resolution andsaid image compression unit performs image compression at the highcompression factor in conformance to instructions issued at saidinstruction unit.
 5. An electronic camera having a continuous shootingfunction, comprising: an image capturing unit that captures a subjectimage; a setting unit that sets operating parameters related to imageprocessing performed during image capturing; a resolution conversionunit that performs resolution conversion image data of an image capturedby said image capturing unit in correspondence to a resolution set atsaid setting unit; an image compression unit that performs imagecompression on image data converted by said resolution conversion unitin correspondence to a compression factor set at said setting unit; anda continuous shooting unit that performs continuous shooting of asubject image by continuously driving said image capturing unit, saidresolution conversion unit and said image compression unit, wherein:said setting unit is capable of setting a continuous shooting speed atsaid continuous shooting unit at least at a normal speed and at a highspeed that is higher than the normal speed; said resolution conversionunit is capable of performing resolution conversion at least at a highresolution and at a low resolution that is lower than the highresolution; said image compression unit is capable of performing imagecompression at least at a low compression factor and a high compressionfactor that is higher than the low compression factor; and when saidcontinuous shooting unit executes continuous shooting, said resolutionconversion unit performs resolution conversion at the low resolution andsaid image compression unit performs image compression at the highcompression factor if the continuous shooting speed is set to the highspeed.
 6. An electronic camera having a continuous shooting functionaccording to claim 3, wherein: an instruction unit that issuesinstructions to ensure that said resolution conversion unit performsresolution conversion at the low resolution and said image compressionunit performs image compression at the high compression factor, withouthaving to change settings for the resolution and the compression factorthat have been set by said setting unit, is provided; and when saidcontinuous shooting unit executes continuous shooting and the continuousshooting speed is set to the high speed, said resolution conversion unitperforms resolution conversion at the low resolution and said imagecompression unit performs image compression at the high compressionfactor in conformance to instructions issued at said instruction unit.7. An electronic camera having a continuous shooting function,comprising: an image capturing unit that captures a subject image; asetting unit that sets operating parameters related to image processingperformed during image capturing; a resolution conversion unit thatperforms resolution conversion on image data of an image captured bysaid image capturing unit in correspondence to a resolution set at saidsetting unit; an image compression unit that performs image compressionon image data converted by said resolution conversion unit incorrespondence to a compression factor set at said setting unit; ad acontinuous shooting unit that performs continuous shooting of a subjectimage continuously driving said image capturing unit, said resolutionconversion unit and said image compression unit, wherein: saidresolution conversion unit is capable of performing resolutionconversion a least at a high resolution and at a low resolution that islower than the high resolution; image compression at least at a lowcompression factor and at a high compression factor that is higher thanthe low compression factor; and when said continuous shooting unitexecutes continuous shooting, said resolution conversion unit performssolution conversion at the low resolution and said image compressionunit performs image compression at the high compression factor.
 8. Anelectronic camera having a continuous shooting function according toclaim 7, wherein: an instruction unit that issues instructions to ensurethat said resolution conversion unit performs resolution conversion atthe low resolution and said image compression unit performs imagecompression at the high compression factor, without having to changesettings for the resolution and the compression factor that have beenset by said setting unit, is provided; and when said continuous shootingunit executes continuous shooting, said resolution conversion unitperforms resolution conversion at the low resolution and said imagecompression unit performs image compression at the high compressionfactor in conformance to instructions issued at said instruction unit.